Motorboat with a skimmer hull

ABSTRACT

The invention concerns a motorboat with a skimmer hull. The hull is a W-shaped cross section and comprises an inverted V-shaped longitudinal central tunnel formed by two median faces of the hull and extending substantially over all the length of the hull, the vertex of this tunnel being level with the waterline.

REFERENCE TO RELATED APPLICATION

[0001] This application is a continuation of the PCT International Application No. PCT/FR01/01277 filed Apr. 25, 2001, which is based on the French Application No. 00-05599 filed Apr. 28, 2000.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The invention relates to a motorboat of the skimmer hull type.

[0004] 2. Description of the Prior Art

[0005] At present, the search for high performance in motorboat racing leads to the use of either deep V hulls, which have a small capacity, low stability at high speeds and high sensitivity to roll, or of the catamaran type, whose marine qualities and performance are appreciated but which also have a small capacity, especially in small sizes, for example from around 6 meters to around 12 meters.

OBJECT OF THE INVENTION

[0006] One particular object of the present invention is to avoid these drawbacks of the prior art whilst retaining or improving on its advantages.

SUMMARY OF THE INVENTION

[0007] Accordingly, the invention proposes a motorboat with a skimmer hull, characterized in that the hull has a W-shaped cross section and comprises an inverted V-shaped longitudinal central tunnel which extends substantially all the length of the hull and whose bottom is substantially level with the waterline.

[0008] The hull according to the invention combines the capacity advantages of a wide V single-hull with the stability and performance advantages of a catamaran and increases the lifting surface area for the same draft and the same width.

[0009] As a corollary of this, the invention increases the width of the hull, for the same length, and consequently the capacity, whilst preserving exactly the same performance and speed potential.

[0010] What is more, the shape of the hull allows beaching in a stable horizontal position, with no risk of lateral tilting.

[0011] According to other features of the invention:

[0012] the bow is truncated, so that the central tunnel can extend to the most forward portion of the hull without significantly changing its shape,

[0013] the angle of the walls of the tunnel is substantially constant over all of the length of the hull,

[0014] the base line of the tunnel can be slightly inclined downwardly from the bow toward the stern, to generate longitudinal lift and improve the horizontal trim of the boat when in motion,

[0015] a hydrofoil type transverse aileron is mounted between the walls of the tunnel in the aft portion of the hull to generate supplementary lift at the stern and to compensate at least partly for the weight of the motors.

[0016] The invention applies generally to motor launches, both civil and military, and to “aquabikes” (sit-down jet skis, stand-up jet skis, etc.), and enables to increase their capacity, stability and performances.

BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The invention will be better understood and other features, details and advantages thereof will become more clearly apparent in the course of the following description, which is given by way of example only and with reference to the accompanying drawings, in which:

[0018]FIG. 1 is a diagrammatic front view of a hull according to the invention;

[0019]FIG. 2 is a bottom view of this hull;

[0020]FIG. 3 is a side view of this hull;

[0021]FIG. 4 is a perspective view of this hull;

[0022]FIG. 5 is a diagrammatic view in cross section of a different embodiment;

[0023]FIGS. 6, 7, 8 and 9 are views corresponding to FIGS. 1 to 4 but representing a further embodiment of the invention;

[0024]FIG. 10 is a diagrammatic front view of a still further embodiment; and

[0025]FIG. 11 is a diagrammatic partial side view corresponding to FIG. 10.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0026] In the embodiment of a hull according to the invention shown in FIGS. 1 to 4, the hull comprises four longitudinal faces 10, 12, 14, 16, i.e. which extend from the forward end to the aft end of the hull and in cross section form a W-shape.

[0027] These faces are substantially plane and symmetrical in pairs with respect to longitudinal vertical planes passing through the vertices of the W-shape. To be more precise, an exterior face 10 and an adjacent median face 12 are symmetrical with respect to a longitudinal vertical plane 18 passing through the vertex of a V-shape formed by the faces 10 and 12, the median faces 12 and 14 are symmetrical with respect to a median longitudinal vertical plane 20, and the median face 14 and the other exterior face 16 are symmetrical with respect to a longitudinal vertical plane 22 passing through the vertex of the V-shape formed by the faces 14 and 16. In the example shown in FIGS. 1 to 4, the angle of the faces 10, 12, 14, 16 to the vertical is approximately 45°. As a general rule, it can be from approximately 40° to approximately 75°. In what is currently the preferred embodiment, this angle is from approximately 55° to approximately 70° and is even more preferably close to 63°.

[0028] The median faces 12 and 14 form an inverted V-shape central tunnel whose vertex 24 is substantially at the same level as the waterline 26 and extends longitudinally at the level of this waterline from the stern to the vicinity of the bow 28, where it rises upwardly.

[0029] The bow 28 is truncated transversely, so that the central tunnel formed by the faces 12 and 14 starts in the most forward part of the hull, and the faces 12 and 14 retain the same angle over virtually all of the length of the hull and flare slightly in the immediate vicinity of the bow.

[0030] As shown diagrammatically, the hull may comprise an exterior step 30 which extends from the stern as far as the vicinity of the bow, but without going right up to the bow. The bow can then have a slightly oval shape for maximum capacity.

[0031] Strakes 32, which either project, as shown in FIG. 1, or are recessed (as shown in FIG. 5) can also be formed on the exterior faces 10 and 16, as well as on the median faces 12 and 14, and extend from the stern as far as the vicinity of the forward end of the exterior step 30. Alternatively, the exterior step 30 and the strakes 32 can extend as far as the immediate vicinity of the bow 28.

[0032] The hull according to the invention has a lifting surface area which is greater than that of a V-shaped hull with the same draft and the same width. The increase is of the order of 25% if the draft is substantially equal to half the width of the hull.

[0033] In the embodiment shown in FIGS. 6 to 9, the hull is again W-shaped in cross section, but the exterior faces 10 and 16 are no longer symmetrical to the median faces 12 and 14 with respect to the respective longitudinal vertical planes 18 and 22, although the median faces 12 and 14 are symmetrical to each other with respect to the median longitudinal vertical plane 20. In the example shown, the angles of the median faces 14, 16 to the vertical are less than the angles of the exterior faces 10, 16 to the vertical.

[0034] The base line 24 of the tunnel formed by the median faces 12 and 14 is substantially rectilinear and level with the waterline 26, but slightly inclined downwardly relative to the horizontal from the bow toward the stern. This slightly increases the angle between the two faces 12 and 14 at the aft end of the hull. This increases the lift acting on the hull at the aft end thereby holding the hull more horizontal when in motion.

[0035] As in the preceding embodiment, exterior steps 30 can be formed on the exterior faces 10, 16 of the hull and extend from the stern to the vicinity of the bow or right up to the bow. Similarly, strakes 32 can be formed on the outside faces 10 and 16 and possibly on the median faces 12 and 14 of the hull.

[0036] In the embodiment shown in FIGS. 10 and 11, which corresponds to the embodiment of FIGS. 1 to 4, the two median faces 14 and 16 of the hull are joined together at the aft end of the hull by a hydrofoil type transverse aileron 34, which is under the water and whose curved profile has its concave side facing downward, to increase the lift at the aft end of the hull and at least partly compensate for the weight of the motors. This aileron can be removably mounted between the faces 14, 16 of the hull.

[0037] Generally speaking, a hull according to the invention has the following advantages, in addition to those already mentioned of improved stability, increased capacity and beaching in a stable horizontal position:

[0038] when stationary, the boat is more stable because of the absence of rolling torque,

[0039] when in motion, because of the water pressure exerted on each of the four faces of the W-shaped hull, the forward end of the hull emerges more easily from the water,

[0040] the lift is increased at the aft end by the features shown in FIGS. 5 to 10 and the boat remains substantially horizontal when in motion, and

[0041] the boat can turn level. 

What we claim is :
 1. A motorboat with a skimmer hull, characterized in that the hull has a W-shaped cross section and comprises an inverted V-shaped longitudinal central tunnel which extends substantially all the length of the hull and whose bottom (24) is substantially level with the waterline.
 2. A boat according to claim 1, characterized in that the width or transverse dimension of the tunnel is substantially constant over all of the length of the hull.
 3. A boat according to claim 1 or claim 2, characterized in that the bow (28) is truncated.
 4. A boat according to any preceding claim, characterized in that the angle of the faces (12, 14) of the tunnel is substantially constant over all of the length of the hull.
 5. A boat according to any preceding claim, characterized in that the angle of the faces (12, 14) of the tunnel increases slightly in the vicinity of the bow.
 6. A boat according to any preceding claim, characterized in that the base line (24) of the tunnel is slightly inclined downwardly from the bow toward the stern.
 7. A boat according to claim 6, characterized in that the angle of the faces (12, 14) of the tunnel increases slightly in the vicinity of the stern.
 8. A boat according to any preceding claim, characterized in that the base line (24) of the tunnel is substantially rectilinear.
 9. A boat according to any preceding claim, characterized in that the longitudinal faces (10, 12, 14, 16) of the hull are substantially symmetrical in pairs with respect to longitudinal vertical planes (18, 20, 22) passing through the junctions of these faces.
 10. A boat according to any of claims 1 to 8, characterized in that the angles between the faces (12, 14) of the tunnel and longitudinal vertical planes passing through the junctions of these faces with the exterior faces (10, 16) of the hull are different from the angles between said exterior faces (10, 16) and those planes.
 11. A boat according to any preceding claim, characterized in that the angles of the faces (10, 12, 14, 16) of the hull to the vertical are from approximately 40° to approximately 75°.
 12. A boat according to any preceding claim, characterized in that an underwater and optionally removable transverse aileron (34) is mounted between the faces (12, 14) of the central tunnel in the aft portion of the boat. 